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Controls on subglacial bedrock bedform development at the base of the Uummannaq Ice Stream, West Greenland

Lane, T.P.; Roberts, D.H.; Rea, B.R.; Ó Cofaigh, C.; Vieli, A.

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Authors

T.P. Lane

B.R. Rea

C. Ó Cofaigh

A. Vieli



Abstract

This paper investigates the controls on the formation of subglacially eroded bedrock bedforms beneath the topographically confined region upstream of the Uummannaq Ice Stream (UIS). During the last glacial cycle, palaeoglaciological conditions are believed to have been similar for all sites in the study, characterised by thick, fast-flowing ice moving over a rigid bedrock bed. Classic bedrock bedforms indicative of glacially eroded terrain were mapped, including p-forms, roches moutonnées, and whalebacks. Bedform long axes and plucked face orientations display close correlation (parallel and perpendicular) to palaeo-ice flow directions inferred from striae measurements. Across all sites, elongation ratios (length to width) varied by an order of magnitude between 0.8:1 and 8.4:1. Bedform properties (length, height, width, and long axis orientation) from four subsample areas, form morphometrically distinct populations, despite their close proximity and hypothesised similarity in palaeoglaciological conditions. Variations in lithology and geological structures (e.g., joint frequency; joint dip; joint orientation; bedding plane thickness; and bedding plane dip) provide lines of geological weakness, which focus the glacial erosion, in turn controlling bedform geometries. Determining the relationship (s) between bedding plane dip relative to palaeo-ice flow and bedform shape, relative length, amplitude, and wavelength has important ramifications for understanding subglacial bed roughness, cavity formation, and likely erosion style (quarrying and/or abrasion) at the ice-bed interface. This paper demonstrates a direct link between bedrock bedform geometries and geological structure and emphasises the need to understand bedrock bedform characteristics when reconstructing palaeoglaciological conditions.

Citation

Lane, T., Roberts, D., Rea, B., Ó Cofaigh, C., & Vieli, A. (2015). Controls on subglacial bedrock bedform development at the base of the Uummannaq Ice Stream, West Greenland. Geomorphology, 231, 301-313. https://doi.org/10.1016/j.geomorph.2014.12.019

Journal Article Type Article
Acceptance Date Dec 12, 2014
Online Publication Date Dec 18, 2014
Publication Date Feb 15, 2015
Deposit Date Mar 1, 2016
Publicly Available Date Mar 28, 2024
Journal Geomorphology
Print ISSN 0169-555X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 231
Pages 301-313
DOI https://doi.org/10.1016/j.geomorph.2014.12.019

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